1. Field of the Invention
The present invention relates generally to a broadcast receiving system which can simultaneously support time-delayed watching of a broadcast program and recording/reproduction of another program, and in particular, to a method of arranging divided recording area segments in a recording medium to allow time-delayed watching of a broadcast program, while another program is being recorded/reproduced.
2. Description of the Related Art
A hard disk drive (HDD) in a computer system is randomly accessible. Due to its advantages of low cost and large capacity relative to other auxiliary memories and a high data transmission rate, the HDD is used as a random access storage device for a broadcast receiving system.
A broadcast receiving system with a random access storage device enables simultaneous recording/reproduction and time-delayed broadcasting of video streams. This can be achieved by controlling buffering of video streams input/output to/from an HDD.
There will be given a description of a method of arranging video streams on a hard disk surface as a recording medium in a broadcast receiving system which supports simultaneous time-delayed watching and recording/reproduction of the video streams.
FIG. 1 illustrates a hard disk managed as a circular buffer in a broadcast receiving system for time-delayed watching, and FIG. 2 illustrates a hard disk managed to record a plurality of video streams uncontinuously.
In the case of a hard disk managed as a circular buffer, video streams are recorded in blocks of a fixed size as shown in FIG. 1. A write point W and a read point R are set on a surface of the hard disk. New video streams are recorded, moving a head clockwise from the write point W, and predetermined video streams are played back by randomly accessing the circular buffer at a specific time.
On the other hand, to uncontinuously arrange video streams on a hard disk drive as shown in FIG. 2, a surface of the hard disk is divided into blocks of a fixed size and video streams are recorded in video files, each including a plurality of blocks. In this case, the blocks are not successively arranged because deletion of video files of different sizes result in uncontinuous free blocks. Information about each video file (title, time information, and so on) and information about the positions of blocks in each video file are recorded in a control information area.
FIGS. 3A through 3D are exemplary I/O (Input/Output) transaction scheduling diagrams for an HDD on/from which video streams are recorded/reproduced in real time. In FIGS. 3A through 3D, three video streams are processed using a C-LOOK algorithm by way of example. The C-LOOK algorithm is similar to a SCAN-Earliest-Deadline-First (SCAN-EDF) scheme disclosed in “I/O Issues in a Multimedia System,” Reddy A. L. N. and Wyllie J. C., IEEE Computer Vol. 27. No. 3, March 1994, pp. 67-74, “Multimedia File Systems Survey: Approaches for Continuous Media Disk Scheduling,” Ralf Steinmetz, Computer Communications, Vol. 18, No. 3, March 1995, pp. 133-144, and a gated operation disclosed in U.S. Pat. No. 5,754,882. Hence, its description is omitted herein.
Referring to FIGS. 3B through 3D, video streams #1 and #2 are being played back and video stream #3 is being recorded. In most video stream processing methods, an HDD I/O control is implemented at every predetermined period T and video streams are processed in each period. For example, if video streams #1 and #2 are read from corresponding blocks on a hard disk surface in period Ti−1, they are played back in period Ti (this corresponds to consumption from a video processor's viewpoint). For continuous reproduction without interruption, blocks to be played back (a process to read data, store the read data in a buffer, and then supply the stored data to a user visibly and/or audibly) in the next period should be read from the HDD in the current period. For recording, blocks should be generated in the current period and then transmitted to the HDD in the next period. The order of processing video streams in a period depends on an I/O transaction scheduling scheme. In the C-LOOK algorithm, the order of processing video streams corresponds to a head moving direction. Assuming that a head of the HDD is moving from an outermost circumferential track to an innermost circumferential track and video stream blocks #1, 2, and 3 are located in tracks #10, 100, and 60, respectively, the video streams #1, 3, and 2 are accessed to read or write in this order in Ti as shown in FIGS. 3A through 3D.
A broadcast receiving system which manages a hard disk area as a circular buffer as shown in FIG. 1 can reproduce a previously recorded video stream with a time delay while recording a current video stream by buffer-controlling data to be input and output to the HDD. However, it cannot record and reproduce a plurality of video streams at the time. In other words, the previously recorded data of a specific channel can not be reproduced while recording a plurality of video streams (i.e., the corresponding broadcast signals to be input from a plurality of channels) since data buffering control is not easy, and is inefficient because of the data access speed of the HDD. In addition, video streams cannot be formed in video file units and an arbitrary video file cannot be deleted.
On the other hand, a broadcast receiving system which arranges video streams uncontinuously as shown in FIG. 2 can store recorded video streams in video files since it can utilize hard disk space freely. But buffer management for time-delayed watching is not easy because blocks are not automatically reused in a limited area as compared to a circular buffer. This is because free blocks are scattered.